In recent years, the application field of an FRP structure is widening to an industrial product field. The reduction of the number of parts and the reduction of the number of assembler steps through integration could be given as the merit of the FRP structure.
When the integration of parts is carried out, there is occasionally a portion where a closed space is formed. When the FRP structure with the closed space should be shaped, a method of applying a pressure in case of shaping and a relation between a jig and the closed space become problems.
For example, in US 2013/0020438A1 (Patent Literature 1), a first fiber preform is arranged on a corrugated jig, as shown in FIG. 25 of Patent Literature 1, and a core (mandrel) covered with a second fiber preform is arranged on the top of the corrugated jig. Then, a fillet shaping jig is arranged and all the things arranged are covered with a third fiber preform. Then, after the laminated preforms and the jigs are wrapped with a suction bag, the inside of the suction bag is evacuated and a matrix resin as a base material is injected into the suction bag. After that, it is coupled to an outer skin, after cutting in a predetermined length through heating and curing.
Also, as a related technique, Patent Literature 2 discloses a method of manufacturing a composite material reinforcing plate. In the manufacturing method disclosed in Patent Literature 2, a first textile material (plate) is first put on a jig having a panel surface shape. Subsequently, a reinforcing material is put on the first textile material. Subsequently, another textile material (second textile material) is arranged on the reinforcing material to cover at least a part of the reinforcing material. Subsequently, the second textile material is shaped to fit the shape of the reinforcing material. Subsequently, the shaped second textile material and the first textile material are stitched along the edge portion of the reinforcing material. Subsequently, the reinforcing material, the first textile material and the second textile material are covered with a bag pack. Subsequently, a resin is introduced or impregnated into each textile material by an RTM method or an RFI method. The impregnated resin is heated to be cured.
A method of shaping a reinforcing panel material is disclosed in Patent Literature 3. In the method of shaping according to Patent Literature 3, a first set of curable composite material sheets is arranged on a jig. Subsequently, each of a plurality of mandrels is wrapped with a corresponding one of a plurality of second curable composite material sheets. Subsequently, the plurality of wrapped mandrels are arranged on the composite material sheets of the first set to be put in parallel to each other. Subsequently, the composite material sheets of the first set and the plurality of second composite material sheets are cured. Subsequently, the mandrels are removed from the cured composite material sheets (the composite material sheets of the first set and the plurality of second composite material sheets).
A method of manufacturing a composite material part is disclosed in Patent Literature 4. In the shaping method according to Patent Literature 4, a first un-cured composite material layer is prepared. Subsequently, at least one hollow mandrel is arranged on the first un-cured composite material layer. Subsequently, a second un-cured composite material layer is arranged on the hollow mandrel and the first un-cured composite material layer. Subsequently, the first un-cured composite material layer and the second un-cured composite material layer are cured in an autoclave.
In the shaping method according to Patent Literature 1, reinforcing fiber preforms are positioned by using the hard core, to shape a small-scale FRP structure. In such a shaping method, it is difficult to shape a large-scale FRP structure using prepreg members superior in dynamics characteristic. Also, according to a difference among the jig, the core and the FRP structure in thermal expansion rate, there is a problem that the size precision is degraded.
FIG. 8 and FIG. 9 are sectional views showing conventional methods of shaping a cylindrical FRP structure. In the method of shaping the FRP structure shown in FIG. 8, a reinforcing fiber 92 is arranged outside a hard core 90 (a hard tool), and the outer circumference of the reinforcing fiber 92 is covered with a suction bag 94. The interior of the suction bag 94 is evacuated. Then, after carrying out heating and curing, the suction bag 94 is removed, and the hard core 90 is pulled out to finish the cylindrical FRP structure. In this shaping method, the hard core 90 exists under the environment of a positive pressure.
In the method of shaping the FRP structure shown in FIG. 9, a reinforcing fiber 92 is arranged inside a hard outer die 91 (a hard tool) and a pressurizing bag 95 is arranged inside the reinforcement fiber 92. Then, the reinforcing fiber 92 is pressurized with the pressurization bag 95. Then, after carrying out heating and curing, the pressurizing bag 95 is removed. Then, a cylindrical FRP structure is pulled out of the hard outer die 91.
In the shaping method shown in FIG. 8, when a closed space does not have a constant sectional shape, but has a complicated shape with a curvature, there are many cases where a releasing process of taking out the hard core 90 from the FRP structure is difficult, after shaping the FRP structure by using the hard core 90. Also, in order to improve the precision of an outer size in case of shaping, it is desirable to use the shaping method shown in FIG. 9. However, when the FRP structure having the complicated form is shaped, there is a problem in the method of pressurizing from the inside of the hard outer die 91. From such a reason, it is difficult to shape an FRP structure with the complicated shape so as to have a plurality of closed spaces.